Optical data recording method and optical disc drive

ABSTRACT

An optical data writing method according to the present invention is designed to write user data optically on an optical disk by dividing the user data into a number of blocks, each being made up of a plurality of sectors, and by adding an error correction code to each block. The method includes the steps of: writing a first set of data, including data representing a first content, on a track on the optical disk; and writing a second set of data, including data representing a second content, onto the track such that an unrecorded area, where no data is stored, is left between respective areas where the first and second sets of data have been written.

TECHNICAL FIELD

The present invention relates to an optical data writing method forwriting data on an optical disk by irradiating the optical disk with alaser beam and also relates to an optical disk drive.

BACKGROUND ART

Recordable optical disks have been the object of much attention as mediathat can store a huge amount of data such as video data. And researchand development has been carried on to increase the capacities of thoserecordable optical disks and store video of higher quality there for alonger time.

Those recordable optical disks are classifiable into disks on which datacan be rewritten a number of times (which will be referred to herein as“rewritable optical disks”) and disks on which data can be added but maybe written only once (which will be referred to herein as “write-onceoptical disks”).

FIG. 1A schematically illustrates the structure of a conventionalwrite-once optical disk. The optical disk 601 includes a spiral track602, on which recording marks 604, obtained by modulating data to bewritten, are made. For example, data representing a first content 603 tobe recorded is modulated, thereby leaving recording marks 604 on theoptical disk 601.

If an unrecorded area is still left even after the first content 603 hasbeen recorded, then data may be further written to the optical disk 601.In writing such data, however, no unrecorded area should be left betweenthe recording marks representing the first content 603 and recordingmarks representing the content to be further written in order to makethe series of recording marks continuous on the track and to read thedata stored properly. As used herein, the “unrecorded area” refers to anarea in which no recording marks are present and which is even longerthan the longest one of the marks and spaces obtained by modulating thedata to be written.

According to a first conventional writing method, to prevent such anunrecorded area from being left between the recorded area and theadditional storage area, the write operation is carried out such thatthe end of the recording marks 604 representing the first content 603 isoverlapped by the beginning of the recording marks 606 representing asecond content 605 as shown in FIG. 1B. As can be seen from FIG. 1B, therecording marks are superposed one upon the other and no marks in propershapes can be left in the area 607. For that reason, dummy data may bewritten on that area 607.

On the other hand, according to a second conventional writing method,the two recording marks are made continuously so as to leave nounrecorded area between the end of the recording marks 604 representingthe first content 603 and the beginning of the recording marks 606representing the second content 605 as shown in FIG. 1C.

According to the first method, however, the recording marks are writtentwice on the same area 607. That is to say, since the area 607 isexposed to an excessive amount of laser beam, the track is likely to bedamaged. As a result, when the written data is read out from such anoptical disk, the focus servo and tracking servo often lose theirstability. Particularly if the first and second contents have beenwritten by using different recorders, then the damage done on the trackmay be significant due to the difference in writing conditions.

Meanwhile, according to the second method, one of the recording marksrepresenting the second content is left adjacent to one of the recordingmarks representing the first content. Accordingly, in recording thesecond content, the end 609 of the recording marks 604 is subject to theheat generated when the recording marks 606 are made. As a result, therecording marks at the end 609 may be deformed or destroyed, which is aproblem.

The higher the storage densities of optical disks, the narrower thetrack pitches and track widths. Then, such a problem will be even morelikely to occur in the near future.

DISCLOSURE OF INVENTION

In order to overcome at least one of the problems described above, anobject of the present invention is to provide an optical data writingmethod and optical disk drive for performing a read operation with goodstability even if a write-once operation has been performed.

An optical data writing method according to the present invention isdesigned to write user data optically on an optical disk by dividing theuser data into a number of blocks, each being made up of a plurality ofsectors, and by adding an error correction code to each block. Themethod includes the steps of: writing a first set of data, includingdata representing a first content, on a track on the optical disk; andwriting a second set of data, including data representing a secondcontent, onto the track such that an unrecorded area, where no data isstored, is left between respective areas where the first and second setsof data have been written.

In one preferred embodiment, the track on the optical disk includes noprepit areas defining addresses.

In another preferred embodiment, the unrecorded area is at least as longas one sector.

In another preferred embodiment, the end of the data representing thefirst content and/or the beginning of the data representing the secondcontent includes dummy data.

In another preferred embodiment, the first set of data includes dummydata after the data representing the first content.

In another preferred embodiment, the second set of data includes dummydata before the data representing the second content.

In another preferred embodiment, a gap as long as one block is providedbetween the respective areas in which the data representing the firstcontent and the data representing the second content have been written.

In another preferred embodiment, each of the first and second sets ofdata is divided into a plurality of sectors, which are spaced apart fromeach other by linking areas of the same length, and a gap as long as onelinking area is provided between the respective areas where the datarepresenting the first content and the data representing the secondcontent have been written.

In another preferred embodiment, the dummy data defines a phase-lockingpattern.

In another preferred embodiment, the first or second set of data iswritten by irradiating the unrecorded area with light having erasingpower.

A computer-readable storage medium according to the present inventionhas stored thereon a program that is defined so as to make a computerexecute respective processing steps of one of the optical data writingmethods described above.

An optical disk drive according to the present invention is designed towrite user data optically on an optical disk by dividing the user datainto a number of blocks, each being made up of a plurality of sectors,and by adding an error correction code to each block. The driveincludes: a motor for rotating and driving the optical disk; an opticalhead for irradiating the optical disk with a light beam to write datathereon; a servo control section for controlling the rotational velocityof the motor and a spot made by the light beam; and a light beam controlsection for controlling the intensity of the light beam. The servocontrol section and the light beam control section control the opticaldisk and the light beam so as to write a first set of data, includingdata representing a first content, on a track on the optical disk andthen write a second set of data, including data representing a secondcontent, onto the track such that an unrecorded area, where no data isstored, is left between respective areas where the first and second setsof data have been written.

In one preferred embodiment, the track on the optical disk includes noprepit areas defining addresses.

In another preferred embodiment, the unrecorded area is at least as longas one sector.

An optical disk according to the present invention is a disk, on a trackof which user data has been written optically by dividing the user datainto a number of blocks, each being made up of a plurality of sectors,and by adding an error correction code to each block. An unrecordedarea, where no data has been written yet, is formed between an areawhere a first set of data, including data representing a first content,is stored and an area where a second set of data, including datarepresenting a second content, is written.

In one preferred embodiment, the track includes no prepit areas definingaddresses.

In another preferred embodiment, the unrecorded area is at least as longas one sector.

BRIEF DESCRIPTION OF DRAWINGS

FIGS. 1A, 1B and 1C schematically illustrate a conventional method toadd data onto an optical disk.

FIG. 2 is a block diagram illustrating a preferred embodiment of anoptical disk drive according to the present invention.

FIGS. 3A and 3B schematically illustrate a first preferred embodiment ofa writing method according to the present invention.

FIG. 4 schematically shows a structure of data to be written on anoptical disk.

FIG. 5 schematically shows another structure of data to be written on anoptical disk.

FIG. 6 schematically shows still another structure of data to be writtenon an optical disk.

FIGS. 7A and 7B schematically illustrate the first preferred embodimentof the writing method of the present invention.

BEST MODE FOR CARRYING OUT THE INVENTION Embodiment 1

Hereinafter, a first preferred embodiment of an optical disk drive andoptical data writing method according to the present invention will bedescribed. The present invention is applicable to an optical disk driveand optical data writing method for making a recording mark byirradiating an optical disk, including a storage layer, with an infraredray, visible radiation, an ultraviolet ray or light with any of variouswavelengths (which may fall within the range of 635 nm to 830 nm or maybe 405 nm) and by changing the reflectance of the irradiated portion.

FIG. 2 is a block diagram illustrating a configuration for an opticaldisk drive 300 according to this preferred embodiment. The optical diskdrive 300 includes a spindle motor 302, an optical head 303, a lightbeam control section 304, a servo control section 305, a read signaldigitizing section 306, a digital signal processing section 307, a writecompensating section 308 and a CPU 309.

The spindle motor 302 rotates and drives an optical disk 101 at apredetermined rotational velocity under the control of the servo controlsection 305.

The servo control section 305 controls the tracking control and focuscontrol operations such that the light beam emitted from the opticalhead 303 follows the track on the optical disk 101 and maintains apredetermined converging state on the track.

In performing a read operation, the optical head 303 irradiates theoptical disk 101 with a light beam and converts the light reflected fromthe optical disk 101 into an electrical signal, thereby outputting it asa read signal. The read signal digitizing section 306 amplifies anddigitizes the read signal supplied from the optical head 303, therebygenerating a digital signal. Also, by using a built-in PLL (not shown),the read signal digitizing section 306 generates a clock signalsynchronized with the digital signal.

The digital signal processing section 307 processes the digital signal.If address information is included in the digital signal, then thedigital signal processing section 307 subjects the digital signal to apredetermined demodulation process, thereby extracting an address fromit. On the other hand, if user data is included in the digital signal,then the digital signal processing section 307 subjects the digitalsignal to a predetermined demodulation process and error correctionprocess, thereby generating read data. The address information and readdata thus obtained are output to a host PC 310.

In writing data on the optical disk 101, the digital signal processingsection 307 receives the data to be written from the host PC 310. Also,the digital signal processing section 307 adds an error correction codeto the write data received and subjects it to a predetermined modulationprocess, thereby generating modulated data.

The modulated data generated is converted by the write compensatingsection 308 into optically modulated data consisting of pulse trains.The write compensating section 308 also finely adjusts the pulse widthsof the optically modulated data, thereby converting it into a writepulse signal, which contributes to making a recording mark easily.

The light beam control section 304 controls the optical head 303 suchthat a light beam corresponding to the write pulse signal is output inaccordance with the instruction of the CPU 309. In this case, the CPU309 instructs the servo control section 305 to control the spot of thelight beam that has been emitted from the optical head 303 and therotational velocity of the optical disk such that the light beam isincident on a predetermined location on the optical disk.

The host PC 310 includes a computer (not shown), an application program(not shown) and an operating system (not shown) and instructs theoptical disk drive 300 to perform a read or write operation.

If a first set of data, including data representing a first content, hasbeen written on a track on an optical disk and if a second set of data,including data representing a second content, is further written ontothat track, the optical disk drive 300 writes the second set of datasuch that an unrecorded area is left between the respective areas wherethe first and second sets of data have been written. Hereinafter, theoptical data writing method performed by this optical disk drive 300will be described in detail.

FIG. 3A schematically illustrates the structure of the optical disk 101on which a first content 103 has been written. The optical disk 101includes a spiral track 102 on which recording marks, representing datato be written, are made. The optical disk 101 is a write-once disk. Asused herein, the “write-once disk” refers to a disk that allows the userto write data only once on an unrecorded area. However, as long as theunrecorded area is still left, the operation of writing data onto thatunrecorded area may be performed in multiple stages. That is to say, thedata does not have to be written on the entire disk at a time.

On the track 102, recording marks 104, representing data representingthe first content 103, have already been left. Also, an unrecorded area108 where no recording marks have been made yet is still left on thetrack 102 and extends from the last one of the recording marks 104 inthe writing direction. Since data is written on a track by making thoserecording marks on the track, “to make a recording mark” will beregarded herein as synonymous with “to write data”.

An information storage management area 110 is provided as the innermostarea on the optical disk 101. The information management area 110includes a power calibration area for calibrating the laser power duringa write operation and a storage management area for managing the storagearea.

In writing the second content 105 onto the optical disk 101 in such astate, an unrecorded area 109 on which no recording marks 109 have beenmade yet is provided between the last one of the recording marks 104representing the first content 103 and the beginning of the secondcontent 105 as shown in FIG. 3B. It should be noted that FIG. 3Bschematically illustrates the structure of the track and does not showthe recording marks and unrecorded area 109 in accordance with theiractual size relationship.

By providing the unrecorded area 109 in this manner, the recording marks104 representing the first content 103 and the recording marks 106representing the second content 105 never overlap with each other. Thus,it is possible to avoid the unwanted situation where the track isdeformed due to the exposure to an excessive amount of radiation.Consequently, the servo operation never loses stability at the boundaryportion and the read/write operations can always be performed with goodstability.

However, the recording marks 104 are preferably made continuously withinthe area in which the data representing the first content 103 should bestored, and the recording marks 106 are preferably made continuouslywithin the area in which the data representing the second content 105should be stored. In that case, the unrecorded area will indicate thelinking portion between the contents, and the gap between the contentscan be detected quickly when data is read out from the optical disk 101.

FIG. 4 schematically shows the structures of the first content 103,second content 105 and unrecorded area 215 to be stored on the track 102on the optical disk 101. Data is written on the track 102 on asector-by-sector basis and error correction process is performed on eachblock consisting of a plurality of sectors. Address informationrepresenting a relative position on the track 102 is also given on ablock-by-block basis.

The address information may be either defined as data by the recordingmarks or superposed on the track wobble. However, the sectors preferablyinclude no header areas in which the address is defined in advance byprepits as in a DVD-RAM, for example. Since no data may usually bewritten on such a header area, the respective sectors will besubstantially separated by those header areas. Thus, even if no suchunrecorded areas are provided, no problems due to the deformation of thetracks or recording marks will arise.

The first content 103 ends with a block 214 including sectors 202 to205, while the second content 105 begins with a block 216 includingsectors 210 to 213. The unrecorded area 109 is preferably provided on ablock basis and may include one block 215, for example. This block 215includes sectors 206 to 209. Since no recording marks are made on theblock 215, it is actually impossible to distinguish the sectors 206 to209. However, an area, which is long enough to store data correspondingto the sectors 206 to 209, is secured along the track 102.

Hereinafter, it will be described with reference to FIGS. 2 and 4 howthe optical disk drive 300 performs read and write operations. A programor firmware that makes the CPU 309 control the respective components ofthe optical disk drive 300 in the procedure to be described below may bestored in a computer-readable storage medium such as an EEPROM, a ROM, aRAM, a hard disk or a magnetic recording medium (none of which isshown).

First, recording marks representing the first content are made on thetrack 102 on the optical disk 101 by a conventional method. While thefirst content is being written, the laser power is calibrated in theinformation management area 110. After the first content has beenwritten, information about the first content (e.g., the end addressthereof) may be stored in the information management area 110.

Next, the second content is written on the optical disk 101. The opticaldisk drive 300 that writes the second content may or may not be the sameas the optical disk drive 300 that has written the first content.

When the host PC 310 requests the CPU 309 to write the second content,the servo control section 305 moves the optical head 303 to around asector having the address requested. In this case, if the optical diskdrive that has written the first content is different from the opticaldisk drive that is going to write the second content, then the laserpower is calibrated in the information management area 110 before thesecond content is written.

Meanwhile, the digital signal processing section 307 modulates thesecond content and the write compensating section 308 finely adjusts thewidths and positions of the pulse signal that has been modulated so asto make appropriate recording marks. To write the second content, thelocation where the write operation should be started needs to bedetected accurately. For that purpose, the optical disk 101 isirradiated with the light and the optical head 303 and read signaldigitizing section 306 acquires the address of the area where the firstcontent has been written by using the digital signal obtained from thereflected light. More specifically, the address reading process isstarted and the sectors 202, 203, 204 and 205 are read, therebydetecting the block address by the wobble information. As a result, thelast block 214 in which the first content 103 has been written can belocated.

The CPU 309 reads the address of the block 215 and starts writing dataon the block 216 from the sector 210 such that the block 215 to be theunrecorded area 109 is left unrecorded after the last block of the firstcontent 103 and that recording marks representing the second content 105start being made on the block 216 that follows the block 215.

In this case, the light beam output from the optical head 303 iscontrolled by the light beam control section 304 to a predeterminedpower value that has been instructed by the CPU 309. Also, by changingthe radiation power of the light beam in accordance with the datagenerated by the write compensating section 308, the opticalcharacteristic of the material of the storage layer is changed, therebymaking predetermined recording marks on the track 102. After data hasbeen written on the sector 210, predetermined data is sequentiallywritten on the sectors 211, 212 and 213 to finish writing the secondcontent 105. When the second content 105 has been written, informationabout the address of the second content 105 may be written on theinformation management area.

In reading the optical disk 101, the optical disk drive 300 irradiatesthe optical disk 101 with a light beam and makes the optical head 303generate a read signal from the light that has been reflected from theoptical disk 101 as in reading a normal read-only optical disk. The readsignal thus obtained is amplified and digitized by the read signaldigitizing section 306, thereby generating a digital signal. In themeantime, a clock signal synchronized with the digital signal isgenerated by the internal PLL (not shown).

The digital signal obtained in this manner has a no-data portion,corresponding to the unrecorded area 109 of the optical disk 101,between the data representing the first content and the datarepresenting the second content. For that reason, if this optical diskwere read by the same signal processing as in reading a normal read-onlyoptical disk, then the unrecorded area might be sensed as a lead-outarea by mistake and the read operation might end without reading thedata representing the second content at all.

To avoid such an error, the optical disk drive 300 maintains aphase-locked state by using the clock signal, generated by the PLL,during the interval after the first content has been read through andbefore the data representing the second content is retrieved. If normaldata is temporarily unavailable due to deposition of dust on an opticaldisk, for example, an optical disk drive usually has the function ofretaining the previous data until the normal data becomes available.Accordingly, by modifying such a function so that the previous data isretained and the digital signal is kept synchronized during the intervalcorresponding to the unrecorded area, the optical disk of the presentinvention can be read appropriately.

In this preferred embodiment, a phase-locking pattern may be provided atthe beginning of a block representing the content. By recording thephase-locking pattern, the PLL can accomplish phase locking quickly andthe read operation can be performed with good stability even if there isan unrecorded area.

Specifically, as shown in FIG. 5, phase-locking patterns 404, 405, 407,408 and 409 may be provided at the respective tops of blocks 401 and214, representing a portion of the first content 103, and blocks 216,204 and 403 representing a portion of the second content 105. Thephase-locking patterns may be provided as an alternation of 4T marks and4T spaces, an alternation of 3T marks and 3T spaces, an alternation of2T marks and 2T spaces, or an alternation of 5T marks and 5T spaces, forexample.

By providing such phase-locking patterns, the optical disk drive 300 canretain the previous data during the interval corresponding to theunrecorded area 215 after having read data from the block 214 of thefirst content 103. And in reading data from the block 216 of the secondcontent 105, the optical disk drive 300 can synchronize the digitalsignal, generated by processing the data of the second content 105,quickly since the phase-locking pattern 216 is provided at the top ofthe block 216.

Also, the phase-locking patterns 404, 405, 408 and 409 provided for theblocks 401, 214, 402 and 403, respectively, can contribute to recoveringthe stability of the phase-locked loop quickly even if the PLL has lostsome of the stability due to a scratch on the track 102, for example.

In addition, another phase-locking pattern 406 may be provided at theend of the last block 214 of the first content 103. In that case, thephase-locking patterns 406 and 407 are arranged before and after theblock 215 representing the unrecorded area. As a result, in the digitalsignal, no-signal portion corresponding to the block 215 is interposedbetween two phase-locking signal components, thus further increasing thestability of the digital signal.

It should be noted that the phase-locking patterns 404, 405, etc.provided at the top of the blocks, the pattern 406 provided at the endof the first content, and the phase-locking pattern 407 provided at thebeginning of the content may have mutually different lengths. Amongother things, the phase-locking pattern 407 provided at the beginning ofthe second content 105 is preferably longer than the phase-lockingpatterns of the other blocks because the pattern 407 is preceded by theunrecorded area.

Furthermore, the pattern provided at the end of the first content 103does not have to be a phase-locking pattern. The optical disk drive canalso sense the end of the first content if the pattern provided at theend of the second content 103 is different from the other patterns.

The optical disk described above includes an unrecorded area that is aslong as one block. However, the unrecorded area may be shorter than oneblock. As shown in FIG. 6, the block 215, sandwiched between the lastblock 214 of the first content 103 and the first block 216 of the secondcontent 105, includes an unrecorded area 220 and dummy data areas 501and 502 on which recording marks, representing arbitrary dummy data,have been written. As used herein, the “dummy data” is data other thanuser data and address data. The dummy data area 501 is adjacent to thelast block 214 of the first content 103, while the dummy data area 502is adjacent to the first block 215 of the second content 105.

In order to prevent making of the recording marks in the dummy dataareas 501 and 502 from affecting the recording marks that form the firstand second contents 103 and 105, the recording marks are preferablywritten in the dummy data area 501 right after the first content 103 hasbeen written fully. Also, the recording marks are preferably left in thedummy area 502 just before the second content 105 starts to be written.

That is to say, a first set of data 525, including the data representingthe first content 103 and the dummy data to be written onto the dummydata area 501, is written onto the track 102 at a time. Next, a secondset of data 526, including the dummy data to be written onto the dummydata area 502 and the data representing the second content 105, iswritten onto the track 102 at a time such that the unrecorded area 220is left between the respective areas where the first and second sets ofdata have been written. As a result, it is possible to prevent the dummydata areas 501 and 502 from affecting the recording marks that form thefirst and second contents 103 and 105 or the overwritten recording marksfrom deforming the track shape.

The dummy data area 501 may form either all or just a part of the sector206. Likewise, the dummy data area 502 may form either all or just apart of the sector 209. Also, if an unrecorded area that is at least aslong as one sector is left, each dummy area may be equal to or longerthan two sectors. Furthermore, unless the recording end point of thedummy area 501 overlaps with the recording start point of the dummy area502, the unrecorded area 220 may even be shorter than one sector.

The dummy data areas 501 and 502 are included in the same block 215.However, data for the dummy data area 501 and data for the dummy dataarea 502 are written at mutually different times. That is why in writingdata on the dummy data area 502, first, the data is preferably read fromthe dummy data area 501 and then an error correction code is preferablyadded to the data that has been written on the dummy data area 501 andto the data that is going to be written on the dummy data area 502.

By providing the dummy data areas 501 and 502, the unrecorded area 220between the two contents can be shortened and the PLL can keep operatingwith even more stability. A phase-locking pattern may be used as thedummy data. To stabilize the operation of the PLL, the dummy data area501 is preferably longer than the dummy data area 502 that is adjacentto the second content 105.

In the preferred embodiment described above, an unrecorded area isprovided between two contents. However, if no marks are recorded in theunrecorded area, the write operation may be performed with higher powerthan that used for a read operation. For example, the write operationmay be performed with erasing power.

Embodiment 2

Hereinafter, a second preferred embodiment of the present invention willbe described. FIGS. 7A and 7B schematically illustrate the structure ofan optical disk on which a first content 603 and a second content 605are stored. As in the first preferred embodiment described above, thisoptical disk is also a write-once disk and has a spiral track 602 onwhich recording marks, representing data to be stored, are made. Aninformation management area is provided in an inside portion of theoptical disk.

Each of the first and second contents 603 and 605 consists of aplurality of blocks, each of which includes a plurality of sectors.Linking areas of the same length are provided between those sectors.

For example, the first content 603 includes sectors 702 to 705 and thesecond content 605 includes sectors 706 to 709. A linking area 712 isprovided between the sectors 704 and 705 and a linking area 716 isprovided between the blocks 706 and 707.

A linking area 717 is provided between the last block 710 of the firstcontent 603 and the first block 711 of the second content 605, i.e.,between the sectors 705 and 706.

A predetermined signal has been written on the linking areas included inthe first and second contents 603 and 605. For example, a phase-lockingsignal may have been written there. On the other hand, the linking area717 between the first and second contents 603 and 605 includes dummydata areas 713 and 715 in which predetermined dummy data is stored andan unrecorded area 714 interposed between the dummy data areas 713 and715.

The dummy data area 713 is adjacent to the sector 705 of the firstcontent 603, while the dummy data area 715 is adjacent to the sector 706of the second content 605. In the dummy data areas 713 and 715, datathat can be easily detected and can be clearly distinguished from theuser data (e.g., an iterative pattern with a single frequency, aniterative pattern with a unique period, or a pattern that is not usedfor writing user data) is preferably stored. By storing such easilydetectable data in the dummy data areas 713 and 715, the boundarybetween the first and second contents 603 and 605 can be located easily.

By providing the unrecorded area 714 in this manner, the recording marksrepresenting the first content 603 and the recording marks representingthe second content 605 never overlap with each other. Thus, it ispossible to avoid the unwanted situation where the track is deformed dueto the exposure to an excessive amount of radiation. Consequently, theservo operation never loses stability at the boundary portion and theread/write operations can always be performed with good stability.

The data stored in the dummy data area 715 may be a phase-lockingpattern. In that case, when a signal representing the second content isread, the PLL can accomplish phase locking by using the phase-lockingpattern. As a result, the second content can be read with goodstability.

Also, the signal written on the dummy data area 713 may be differentfrom that written on the dummy data area 715. Then, the boundary betweenthe first and second contents 603 and 605 can be located. Furthermore,by detecting both the dummy data areas 713 and 715 and the unrecordedarea, the temporary absence of signals due to dust deposited on theoptical disk, for example, and the unrecorded area in the boundarybetween the two contents can be distinguished from each other.

Optionally, the length of the signal written on the dummy data area 713may be different from that of the signal written on the dummy data area715. In that case, even if the same signal as that stored in the dummydata area 713 or 715 is included in the user data, the boundary betweenthe two contents can still be detected by the difference between thelengths of signals that have been written on the dummy data areas 713and 715.

If a phase-locking pattern is included in the data stored in the dummydata area 715, then the signal written on the dummy data area 715 ispreferably longer than that written on the dummy data area 713. In thatcase, when a signal representing the second content is read, the PLL canaccomplish phase locking by using the phase-locking pattern. As aresult, the second content can be read with good stability.

The writing method of this preferred embodiment may be carried out byusing the optical disk drive 300 that has already been described for thefirst preferred embodiment. Hereinafter, it will be described withreference to FIGS. 2, 7A and 7B how the optical disk drive 300 performsread and write operations.

First, a first set of data 725, including the data representing thefirst content 603 and the dummy data to be stored in the dummy data area713, is written on the track 602 on the optical disk. More specifically,the data representing the first content 603 is written first, and thedata for the dummy data area 603 is written immediately. In themeantime, the laser power is calibrated in the information managementarea to start the write operation. After the first content 603 has beenwritten, information including the end address of the first content maybe written on the information management area.

Next, a second set of data 726, including the dummy data to be stored inthe dummy data area 715 and the data representing the second content605, is written on the same track 602 on the optical disk. When the hostPC 310 requests the CPU 309 to write the second set of data, the servocontrol section 305 moves the optical head 303 to around a sector havingthe address requested. In this case, if the optical disk drive that haswritten the first content 603 is different from the optical disk drivethat is going to write the second content 605, then the laser power iscalibrated in the information management area 110 before the secondcontent is written.

Meanwhile, the digital signal processing section 307 modulates thesecond set of data and the write compensating section 308 finely adjuststhe widths and positions of the pulse signal that has been modulated soas to make appropriate recording marks. To write the second set of dataincluding the second content 605, the location where the write operationshould be started needs to be detected accurately. For that purpose, theoptical disk is irradiated with light and the optical head 303 and readsignal digitizing section 306 acquire the address of the area where thefirst content 603 and the dummy data have been written by using thedigital signal obtained from the reflected light. More specifically, theaddress reading process is started and the sectors 702, 703, 704 and 705are read, thereby detecting the block address by the wobble information.As a result, the last block 710 in which the first content 603 has beenwritten can be located.

The CPU 309 leaves the unrecorded area 714 unrecorded after the dummydata area 713, which was provided when the first content 603 waswritten, makes recording marks in the dummy data area 715 in the linkingarea 717, and then starts to write data on the sector 706 and so on.

In this case, the light beam output from the optical head 303 iscontrolled by the light beam control section 304 to a predeterminedpower value that has been instructed by the CPU 309. Also, by changingthe radiation power of the light beam in accordance with the datagenerated by the write compensating section 308, the opticalcharacteristic of the material of the storage layer is changed, therebymaking predetermined recording marks on the track 602. After data hasbeen written on the sector 706, the linking area 716 is defined and thenpredetermined data is sequentially written on the sector 707, linkingarea 716, sector 707 and so on to finish writing the second content 105.When the second content 105 has been written, information about theaddress of the second content 105 may be written on the informationmanagement area.

In reading the optical disk 101, the optical disk drive 300 irradiatesthe optical disk 101 with a light beam and makes the optical head 303generate a read signal from the light that has been reflected from theoptical disk 101 as in reading a normal read-only optical disk. The readsignal thus obtained is amplified and digitized by the read signaldigitizing section 306, thereby generating a digital signal. In themeantime, a clock signal synchronized with the digital signal isgenerated by the internal PLL (not shown). The digital signal obtainedin this manner has a no-data portion, corresponding to the unrecordedarea 109 of the optical disk 101, between the data representing thefirst content and the data representing the second content. For thatreason, if this optical disk were read by the same signal processing asin reading a normal read-only optical disk, then the unrecorded areamight be sensed as a lead-out area by mistake and the read operationmight end without reading the data representing the second content atall.

To avoid such an error, the optical disk drive 300 maintains aphase-locked state by using the clock signal, generated by the PLL,during the interval after the first content has been read through andbefore the data representing the second content is retrieved as in thefirst preferred embodiment described above. If the dummy data stored inthe dummy data areas 713 and 715 is a phase-locking pattern, then theno-signal portion corresponding to the unrecorded area 714 is sandwichedbetween two phase-locking signals. As a result, the read operation canbe performed with more stability.

According to the preferred embodiments described above, an unrecordedarea is provided between a series of two contents, thereby avoiding anunwanted situation where recording marks, representing the content thathas already been written, or the track is deformed due to the heatgenerated while recording marks representing the content to be added arebeing made. Consequently, the written data can be read with goodstability.

In particular, even when the two contents are written by two differentdrives, it is also possible to prevent the problem that the track isdeformed due to the application of significantly excessive heat as therecording marks are overwritten one upon the other.

The writing method of this preferred embodiment is applicableparticularly effectively to a write-once optical disk on which no datais supposed to be written on the same area again or every previous datais supposed to be destroyed whenever any data is written there for thesecond time. According to this writing method, no data is written on thesame area again. That is why the writing conditions can be set withoutbeing limited by the conditions for write-once operation. As a result,the storage layer of an optical disk can be designed much more freely.Also, when an optical disk is disposed of, data may be overwritten thereintentionally such that the servo operation will lose its stability andthat no data can be read out anymore. In this manner, the optical diskcan be thrown away with confidentiality maintained.

Also, no blocks but the first or last one of a content are adjacent tothe unrecorded area. Thus, the gap between the contents can be detectedeasily.

Furthermore, as user data may be written on a block including theunrecorded area, the storage area can be used more effectively.

Besides, when dummy data is stored on a block including the unrecordedarea, the length of the unrecorded area can be shortened and the PLL canoperate with more stability. What is more, if the dummy data is aphase-locking pattern, then the PLL can operate with even morestability.

In the preferred embodiments described above, the unrecorded area issupposed to be provided between two continuous contents. However, theunrecorded area does not have to be provided between two contents.Similar effects are achieved even if the unrecorded area is provided inthe boundary between two sets of data that were written by two differentrecorders or in the boundary between two sets of data that were writtenby the same drive on different occasions.

INDUSTRIAL APPLICABILITY

The present invention can be used effectively in an optical disk drivethat performs a write operation using light sources with variouswavelengths, and is particularly effectively applicable to an opticaldisk drive that can write data on a write-once optical disk.

1. An optical data writing method for writing user data optically on anoptical disk by dividing the user data into a number of blocks, eachbeing made up of a plurality of sectors, and adding an error correctioncode to each said block, the method comprising the steps of: writing afirst set of data, including data representing a first content, on atrack on the optical disk; and writing a second set of data, includingdata representing a second content, onto the track such that anunrecorded area, where no data is stored, is left between respectiveareas where the first and second sets of data have been written.
 2. Theoptical data writing method of claim 1, wherein the track on the opticaldisk includes no prepit areas defining addresses.
 3. The optical datawriting method of claim 1, wherein the unrecorded area is at least aslong as one sector.
 4. The optical data writing method of claim 1,wherein the end of the data representing the first content and/or thebeginning of the data representing the second content includes dummydata.
 5. The optical data writing method of claim 1, wherein the firstset of data includes dummy data after the data representing the firstcontent.
 6. The optical data writing method of claim 1, wherein thesecond set of data includes dummy data before the data representing thesecond content.
 7. The optical data writing method of claim 5, wherein agap as long as one block is provided between the respective areas inwhich the data representing the first content and the data representingthe second content have been written.
 8. The optical data writing methodof claim 5, wherein each of the first and second sets of data is dividedinto a plurality of sectors, which are spaced apart from each other bylinking areas of the same length, and wherein a gap as long as onelinking area is provided between the respective areas where the datarepresenting the first content and the data representing the secondcontent have been written.
 9. The optical data writing method of claim4, wherein the dummy data defines a phase-locking pattern.
 10. Theoptical data writing method of claim 1, wherein the first or second setof data is written by irradiating the unrecorded area with light havingerasing power.
 11. A computer-readable storage medium having storedthereon a program that is defined so as to make a computer executerespective processing steps of the optical data writing method ofclaim
 1. 12. An optical disk drive for writing user data optically on anoptical disk by dividing the user data into a number of blocks, eachbeing made up of a plurality of sectors, and adding an error correctioncode to each said block, the drive comprising: a motor for rotating anddriving the optical disk; an optical head for irradiating the opticaldisk with a light beam to write data thereon; a servo control sectionfor controlling the rotational velocity of the motor and a spot made bythe light beam; and a light beam control section for controlling theintensity of the light beam, wherein the servo control section and thelight beam control section control the optical disk and the light beamso as to write a first set of data, including data representing a firstcontent, on a track on the optical disk and then write a second set ofdata, including data representing a second content, onto the track suchthat an unrecorded area, where no data is stored, is left betweenrespective areas where the first and second sets of data have beenwritten.
 13. The optical disk drive of claim 12, wherein the track onthe optical disk includes no prepit areas defining addresses.
 14. Theoptical disk drive of claim 12, wherein the unrecorded area is at leastas long as one sector.
 15. An optical disk, on a track of which userdata has been written optically by dividing the user data into a numberof blocks, each being made up of a plurality of sectors, and adding anerror correction code to each said block, wherein an unrecorded area,where no data is stored, is provided between an area where a first setof data, including data representing a first content, is stored and anarea where a second set of data, including data representing a secondcontent, is written.
 16. The optical disk of claim 15, wherein the trackincludes no prepit areas defining addresses.
 17. The optical disk ofclaim 15, wherein the unrecorded area is at least as long as one sector.18. The optical data writing method of claim 6, wherein a gap as long asone block is provided between the respective areas in which the datarepresenting the first content and the data representing the secondcontent have been written.
 19. The optical data writing method of claim6, wherein each of the first and second sets of data is divided into aplurality of sectors, which are spaced apart from each other by linkingareas of the same length, and wherein a gap as long as one linking areais provided between the respective areas where the data representing thefirst content and the data representing the second content have beenwritten.